When might sheltering in place not be the best option?

Sheltering in place is generally a safety strategy used to protect the populace from hazardous materials or environments. In situations where vapors or gases are explosive, sheltering in place might not be advisable because being inside a structure can increase the risk of an explosion. The confined space can lead to the accumulation of explosive concentrations of gases or vapors, which could ignite due to sparks, heat, or other ignition sources.

In contrast, moving away from the area where the explosion risk is present would reduce exposure to the explosive hazards. Therefore, when there are explosive vapors or gases, the likelihood of a dangerous situation increases, making evacuation or finding a location with better safety conditions a more effective course of action. In this way, understanding the properties of the hazardous material and the potential risks involved is crucial for determining the most appropriate response strategy.